1. Technical Field
The present invention relates to a transported material transporting device configured to reverse a material to be transported, such as a printed material transported by transporting rollers with a first surface faced in one direction, by switching the direction of rotation of the discharging rollers between a normal rotation and a reverse rotation and transport the same with a second surface of the material to be transported faced in the one direction and, more specifically, to the transported material transporting device which is configured to be able to switch the state of the discharging rollers between a nipped state and a released state at optimal timings irrespective of the length of the material to be transported, and an image processing apparatus having the transported material transporting device.
2. Related Art
As described in JP-A-2007-230657, image scanning devices such as copying machines, facsimile machines or scanners having an Auto Document Feeder as an example of a transported material transporting device are already developed. The image scanning devices as shown above include image scanning devices which are capable of scanning image data recorded on both front and rear surfaces of a material to be transported (hereinafter, referred to also as “paper”) continuously. The image scanning devices described above are configured to guide a paper delivered with a first surface thereof up into a semi-loop shaped transport path, in which the transporting roller, an image scanning portion, and the discharging roller are disposed, transport the paper with the first surface down, and perform image scanning of the first surface.
Subsequently, the image scanning device switches the direction of transport to guide the paper into a reversing path and guides the same again into the transport path, thereby transporting the paper with a second surface, which is an opposite surface from the first surface, faced down, and performs image scanning of the second surface.
Switching of the direction of paper transport and switching of the state of the discharging roller between the nipped state and the released state, which are required when performing the image scanning continuously over the first surface and the second surface of the above-described paper, are performed by the transported material transporting device (hereinafter, referred to also as “paper transporting device” at preset certain timings.
The paper transport path is downsized in accordance with a tendency of downsizing of the image scanning devices, so that the length of the transport path is reduced. Therefore, when transporting a long paper, a portion of a paper delivered to the reversing path and a portion of the paper discharged out from the transport path pass each other at a nip of the discharging rollers during the transport of the second surface. Therefore, the discharging rollers are brought into the released state at the timing when the portions of the paper pass each other as described above, thereby allowing the both to pass each other.
JP-A-2007-230657 and JP-A-2004-2024 are examples of related art.
However, if the switching of the direction of transport of the paper and the switching of the state of the discharging rollers between the nipped state and the released state are performed uniformly at the preset certain timings, the length of the paper that can be provided for the double-sided scanning is limited. If a paper having a length other than those supported by the paper transporting device operated at the certain timings, transport failures such as skewing or jamming of the paper may be resulted.
It is also possible to perform the switching of the state of the discharging rollers between the nipped state and the released state separately from powers of the transporting roller and the discharging roller using a separate power, for example, a solenoid or the like which is disclosed in JP-A-2004-2024. However, it results in increase in number of components and complicated structure, thereby leading to the cost of the paper transporting device.